Four cycle engine for marine drive

ABSTRACT

An engine has a combustion chamber. An air induction system communicates with the combustion chamber through an intake port. An exhaust system communicates with the combustion chamber through an exhaust port. Intake and exhaust valves move between an opening position and a closing position of the intake port and the exhaust port, respectively. A camshaft actuates either the intake valve or the exhaust valve. The camshaft extends generally vertically. A camshaft cover member encloses the camshaft together with an engine body of the engine. The camshaft cover member defines a slot through which a tool can pass. The tool can prevent the camshaft from rotating.

PRIORITY INFORMATION

[0001] This application is based on and claims priority to JapanesePatent Application No. 2001-223982, filed Jul. 25, 2001, the entirecontents of which is hereby expressly incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to a four-cycle enginefor a marine drive, and more particularly to a four-cycle engine for amarine drive that has a vertically extending camshaft.

[0004] 2. Description of Related Art

[0005] Marine drives such as an outboard motors include a marinepropulsion device powered by an engine. The propulsion device typicallyis a propeller and is submerged when an associated watercraft rests on abody of water. The outboard motor can employ either a two-cycle engineor a four-cycle engine. Recently, however, many outboard motors havebeen offered with four-cycle engines because they provide betteremissions control.

[0006] Typically, a four-cycle engine includes one or more intake andexhaust valves moving between an open position and a closed positionwithin a cylinder head member. One or more camshafts can be provided toactuate the valves in a timed manner. When the intake valves are open,air is introduced into combustion chambers of the engine through theintake ports. When the exhaust valves are open, exhaust gases aredischarged from the combustion chambers through the exhaust ports.

[0007] The camshafts typically extend vertically within the engine of anoutboard motor. The camshafts are driven by a crankshaft of the enginewhich also extends vertically. The camshafts and the crankshaft can beprovided with sprockets or pulleys around which a timing chain or beltis wound so that the crankshaft drives the camshafts through the timingchain or belt.

[0008] The camshafts can be disposed within a single camshaft chamber orseparate camshaft chambers. A camshaft cover member or members togetherwith the cylinder head member define the chamber or chambers. Normally,some lubricant oil collects in the camshaft chambers after lubricatingother engine portions.

[0009] During certain maintenance and repair procedures, the sprocketsor pulleys need to be removed from the camshafts and then re-attachedafterwards. However, during such procedures, the camshafts should beprevented from rotating. Thus, the camshaft cover member typically isdisconnected from the cylinder head member so a tool can be connected tothe camshaft so as to prevent rotation thereof. Accordingly, the oilwithin the camshaft chambers can spill out when the covers are removed,and thereby stain the engine. Thus, the repairperson should pay specialattention not to stain the engine with the oil.

[0010] Additionally, in some arrangements, the camshaft cover member canbe nested in a space defined between the sprocket or pulley and thecamshaft so as to shorten the outboard motor in height. If the camshaftcover member is necessary to be removed in this arrangement, thesprocket or pulley should be disassembled first. The camshaft isrequired not to rotate for the disassembling service of the sprocket orpulley. For instance, the timing chain or belt can be fixed by a certaintool so that the camshaft does not rotate. However, the service isextremely difficult because the outboard motor can only afford a limitedspace for the service.

SUMMARY OF THE INVENTION

[0011] A need therefore exists for an improved four-cycle engine for amarine drive that can provide good serviceability of a camshaft and/orcomponents around the camshaft.

[0012] In accordance with one aspect of the present invention, aninternal combustion engine for a marine drive comprises an engine body.A movable member is movable relative to the engine body. The engine bodyand the movable member together define a combustion chamber. The enginebody defines intake and exhaust ports communicating with the combustionchamber. An air induction system communicates with the combustionchamber through the intake port. An exhaust system communicates with thecombustion chamber through the exhaust port. An intake valve is arrangedto move between an open position and a closed position. An exhaust valveis arranged to move between an open position and a closed position. Acamshaft is configured to actuate either the intake valve or the exhaustvalve. The camshaft extends generally vertically. A member is arrangedto enclose the camshaft together with the engine body. The memberdefines an opening through which a tool is capable to pass. The tool isadapted to prevent the camshaft from rotating.

[0013] In accordance with another aspect of the present invention, amarine drive comprises an internal combustion engine. A cowling assemblyis configured to surround the engine. The engine comprises an enginebody. A movable member is movable relative to the engine body. Theengine body and the movable member together define a combustion chamber.The engine body defines intake and exhaust ports communicating with thecombustion chamber. An air induction system communicates with thecombustion chamber through the intake port. An exhaust systemcommunicates with the combustion chamber through the exhaust port. Anintake valve is arranged to move between an open position and a closedposition. An exhaust valve is arranged to move between an open positionand a closed position. A camshaft is configured to actuate either theintake valve or the exhaust valve. The camshaft extends generallyvertically. A member is arranged to enclose the camshaft together withthe engine body. The member defines an opening. The cowling assemblycomprises top and bottom cowling members. The top cowling member isdetachably coupled with the bottom cowling member. The opening isdisposed above a top end of the bottom cowling member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and other features, aspects and advantages of the presentinvention are described below with reference to the drawings of severalpreferred embodiments, which are intended to illustrate and not to limitthe invention. The drawings comprise eleven figures.

[0015]FIG. 1 is a side elevational view of an outboard motor configuredin accordance with a preferred embodiment of the present invention. Anengine and drive train are illustrated in phantom.

[0016]FIG. 2 is an enlarged partial sectional and port side elevationalview of a power head of the outboard motor. A camshaft drive mechanismis omitted in this figure except for an intake camshaft sprocket.

[0017]FIG. 3 is a top plan view of the power head. A cowling assembly isshown in section. The engine is partially illustrated in section.

[0018]FIG. 4 is a rear elevational view of the power head. The cowlingassembly is shown in section.

[0019]FIG. 5 is an enlarged, partial sectional and top plan view of theengine illustrating part of an intake system, part of a fuel injectionsystem and a fuel pump assembly of the fuel injection system.

[0020]FIG. 6 is an enlarged, partial sectional and side elevational viewof the engine illustrating a VVT mechanism thereof.

[0021]FIG. 7 is a sectional view of the VVT mechanism taken along theline 7-7 of FIG. 6.

[0022]FIG. 8 is a sectional view of the VVT mechanism taken partiallyalong the line 8-8 of FIG. 6.

[0023]FIG. 9 is a schematic view of a control system of the VVTmechanism.

[0024]FIG. 10 is an enlarged, partial sectional and top plan view of theengine illustrating an arrangement of a camshaft angle position sensor.

[0025]FIG. 11 is an enlarged, partial sectional and top plan view of theengine illustrating a preferred arrangement of a maintenance serviceslot.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0026] With reference to FIGS. 1-6, an overall construction of anoutboard motor 30 that employs an internal combustion engine 32configured in accordance with certain features, aspects and advantagesof the present invention is described below. The engine 32 hasparticular utility in the context of a marine drive, such as theoutboard motor, and thus is described in the context of an outboardmotor. The engine 32, however, can be used with other types of marinedrives (i.e., inboard motors, inboard/outboard motors, jet drives, etc.)and also certain land vehicles. In any of these applications, the engine32 can be oriented vertically or horizontally. Furthermore, the engine32 can be used as a stationary engine for some applications as isapparent to those of ordinary skill in the art in light of thedescription herein.

[0027] The outboard motor 30 generally comprises a drive unit 34, abracket assembly 36, and a marine propulsion device 41. The bracketassembly 36 supports the drive unit 34 on a transom 38 of an associatedwatercraft 40 and places the marine propulsion device 41 in a submergedposition when the watercraft 40 rests on a surface of a body of waterWL. The bracket assembly 36 preferably comprises a swivel bracket 42, aclamping bracket 44, a steering shaft and a pivot pin 46.

[0028] The steering shaft typically extends through the swivel bracket42 and is affixed to the drive unit 34 by top and bottom mountassemblies 43. The steering shaft is pivotally journaled for steeringmovement about a generally vertically extending steering axis definedwithin the swivel bracket 42. The clamping bracket 44 comprises a pairof bracket arms that are spaced apart from each other and that areaffixed to the watercraft transom 38. The pivot pin 46 completes a hingecoupling between the swivel bracket 42 and the clamping bracket 44. Thepivot pin 46 extends through the bracket arms so that the clampingbracket 44 supports the swivel bracket 42 for pivotal movement about agenerally horizontally extending tilt axis defined by the pivot pin 46.The drive unit 34 thus can be tilted or trimmed about the pivot pin 46.

[0029] As used through this description, the terms “forward,”“forwardly” and “front” mean at or toward the side where the bracketassembly 36 is located, and the terms “rear,” “reverse,” “backwardly”and “rearwardly” mean at or toward the opposite side of the front side,unless indicated otherwise or otherwise readily apparent from thecontext use.

[0030] A hydraulic tilt and trim adjustment system 48 preferably isprovided between the swivel bracket 42 and the clamping bracket 44 fortilt movement (raising or lowering) of the swivel bracket 42 and thedrive unit 34 relative to the clamping bracket 44. Otherwise, theoutboard motor 30 can have a manually operated system for tilting thedrive unit 34. Typically, the term “tilt movement”, when used in a broadsense, comprises both a tilt movement and a trim adjustment movement.

[0031] The illustrated drive unit 34 comprises a power head 50 and ahousing unit 52. The housing unit 52 includes a driveshaft housing 54and a lower unit 56. The power head 50 is disposed atop the drive unit34 and includes the internal combustion engine 32 and a protectivecowling assembly 60.

[0032] Preferably the protective cowling 60 is made of plastic anddefines a generally closed cavity 62 (FIGS. 2-4) in which the engine 32is disposed. That is, the cowling assembly 60 surrounds the engine 32.The protective cowling assembly 60 preferably comprises a top cowlingmember 64 and a bottom cowling member 66. The top cowling member 64preferably is detachably affixed to the bottom cowling member 66 by acoupling mechanism 68. When the top cowling member 64 is detached, auser, operator, mechanic or repairperson can access the engine 32 formaintenance or for other purposes.

[0033] With reference to FIG. 2, the top cowling member 64 preferablyhas a rear intake opening 72 on its rear and top portion. A rear intakemember 74 with a rear air duct 76 is affixed to the top cowling member64. The rear intake member 74, together with the rear top portion of thetop cowling member 64, forms a rear air intake space 78. With particularreference to FIG. 4, the rear air duct 76 preferably is disposed to thestarboard side of a central portion of the rear intake member 74.

[0034] With reference to FIG. 2, the top cowling member 64 also definesa recessed portion 82 at a front end thereof An opening 84 is definedalong a portion of the recessed portion 82 on the starboard side. Theopening 84 extends into the interior of the top cowling member 64. Anouter shell 86 is disposed over the recessed portion 82 to define afront air intake space 88. A front air duct 90 is affixed to therecessed portion 82 of the top cowling member 64 and extends upward fromthe opening 84. In this manner, the air flow path into the closed cavity62 can include an elevated entrance from the front air intake space 88.The air duct 90 preferably has a plurality of apertures 92, each ofwhich preferably is cylindrical.

[0035] A front intake opening (not shown) preferably is defined betweenthe recessed portion 82 of the top cowling member 82 and the outer shell86 so that the front intake space 88 communicates with outside of thecowling assembly 60. Ambient air thus is drawn into the closed cavity 62through the rear intake opening 72 or the front intake opening (notshown) and further through the air ducts 76, 90. Typically, the topcowling member 64 tapers in girth toward its top surface, which is inthe general proximity of the air intake opening 72.

[0036] The bottom cowling member 66 preferably has an opening 96 (FIG.2) through which an upper portion of an exhaust guide member 98 (FIG. 1)extends. The exhaust guide member 98 preferably is made of aluminumalloy and is affixed atop the driveshaft housing 54. The bottom cowlingmember 66 and the exhaust guide member 98 together generally form atray. The engine 32 is placed onto this tray and is affixed to theexhaust guide member 98. The exhaust guide member 98 also has an exhaustpassage through which burnt charges (e.g., exhaust gases) from theengine 32 are discharged.

[0037] With reference to FIGS. 2-5, the engine 32 in the illustratedembodiment preferably operates on a four-cycle combustion principle. Theengine 32 has a cylinder block 102. The presently preferred cylinderblock 102 defines four in-line cylinder bores 104 which extend generallyhorizontally and which are generally vertically spaced from one another.As used in this description, the term “horizontally” means that thesubject portions, members or components extend generally in parallel tothe water line WL when the associated watercraft 40 is substantiallystationary with respect to the water line WL and when the drive unit 34is not tilted and is placed in the position shown in FIG. 1. The term“vertically” in turn means that portions, members or components extendgenerally normal to those that extend horizontally.

[0038] This type of engine, however, merely exemplifies one type ofengine on which various aspects and features of the present inventioncan be suitably used. Engines having other numbers of cylinders andhaving other cylinder arrangements (V, W, opposing, etc.) also canemploy various features, aspects and advantages of the presentinvention. In addition, the engine can be formed with separate cylinderbodies rather than a number of cylinder bores formed in a cylinderblock. Regardless of the particular construction, the engine preferablycomprises an engine body that includes at least one cylinder bore 104.

[0039] A moveable member, such as a reciprocating piston 106, movesrelative to the cylinder block 102 in a suitable manner. One piston 106reciprocates within each cylinder bore 104.

[0040] A cylinder head member 108 is affixed to one end of the cylinderblock 102 to close one end of the cylinder bores 104. The cylinder headmember 108, together with the associated pistons 106 and cylinder bores104, preferably defines four combustion chambers 110. Of course, thenumber of combustion chambers can vary, as indicated above.

[0041] A crankcase member 112 closes the other end of the cylinder bores104 and, together with the cylinder block 102, defines a crankcasechamber 114. A crankshaft or output shaft 118 extends generallyvertically through the crankcase chamber 114 and can be journaled forrotation by several bearing blocks (not shown). A center vertical planeVP FIG. 3) of the outboard motor 30 extends generally vertically andfore to aft through the cylinder block 102, the cylinder head member108, and the crankcase member 112. The verticle plane VP preferablyincludes a longitudinal axis of the crankshaft 118. Connecting rods 120couple the crankshaft 118 with the respective pistons 106 in anysuitable manner. Thus, the crankshaft 118 can rotate with the reciprocalmovement of the pistons 106.

[0042] Preferably, the crankcase member 112 is located at theforward-most position of the engine 32, with the cylinder block 102 andthe cylinder head member 108 being disposed rearward from the crankcasemember 112. Generally, the cylinder block 102 (or individual cylinderbodies), the cylinder head member 108, and the crankcase member 112together define an engine body 124. Preferably, at least these majorengine portions 102, 108, 112 are made of an aluminum alloy. Thealuminum alloy advantageously increases strength over cast iron whiledecreasing the weight of the engine body 124.

[0043] The engine 32 also comprises an air induction system or device126. The air induction system 126 draws air from within the cavity 62 tothe combustion chambers 110. The air induction system 126 preferablycomprises eight intake ports 128, four intake passages 130 and a singleplenum chamber 132. In the illustrated arrangement, two intake ports 128are allotted to each combustion chamber 110 and the two intake ports 128communicate with a single intake passage 130.

[0044] The intake ports 128 are defined in the cylinder head member 108.Intake valves 134 are slidably disposed at the intake ports 128 withinthe cylinder head member 108 to move between an open position and aclosed position. As such, the valves 134 act to open and close the ports128 to control the flow of air into the combustion chamber 110.

[0045] Biasing members, such as springs 136 (FIGS. 5 and 6), are used tobias the intake valves 134 toward the respective closed positions byacting against a mounting boss formed on the illustrated cylinder headmember 108 and a corresponding retainer 138 that is affixed to each ofthe valves 134. When each intake valve 134 is in the open position, theintake passage 130 that is associated with the intake port 128communicates with the associated combustion chamber 110.

[0046] With reference to FIGS. 3 and 5, each intake passage 130preferably is defined by an intake manifold 140, a throttle body 142 andan intake runner 144. The intake manifold 140 and the throttle body 142preferably are made of aluminum alloy. The intake runner 144 preferablyis made of plastic. A portion of the illustrated intake runner 144extends forwardly alongside of and to the front of the crankcase member112.

[0047] With continued reference to FIG. 3, the respective portions ofthe intake runners 144, together with a plenum chamber member 146,define the plenum chamber 132. Preferably, the plenum chamber member 146also is made of plastic.

[0048] The plenum chamber 132 comprises an air inlet 148. The air in thecavity 62 is drawn into the plenum chamber 132 through the air inlet148. The air is then passed through intake passages 130, the throttlebody 142 and the intake manifold 140. Preferably, the plenum chamber 132is configured to attenuate noise generated by the flow of air into therespective combustion chambers 110, and thus act as an “intakesilencer.”

[0049] Each illustrated throttle body 142 includes a butterfly typethrottle valve 152 journaled for pivotal movement about an axis definedby a generally vertically extending valve shaft 154. Each valve shaft154 can be coupled with the other valve shafts to allow simultaneousmovement. The valve shaft 154 is operable by the operator through anappropriate conventional throttle valve linkage and a throttle leverconnected to the end of the linkage. The throttle valves 152 are movablebetween an open position and a closed position to meter or regulate anamount of air flowing through the respective air intake passages 130.Normally, the greater the opening degree, the higher the rate of airflowand the higher the power output of the engine.

[0050] In order to bring the engine 32 to idle speed and to maintainthis speed, the throttle valves 152 generally are substantially closed.Preferably, the valves are not fully closed in the idle position so asto produce a more stable idle speed and to prevent sticking of thethrottle valves 152 in the closed position. As used through thedescription, the term “idle speed” generally means a low engine speedthat achieved when the throttle valves 152 are closed but also includesa state such that the valves 152 are slightly more open to allow arelatively small amount of air to flow through the intake passages 130.

[0051] The air induction system 126 preferably includes an auxiliary airdevice (AAD) (not shown) that bypasses the throttle valves 152 andextends from the plenum chamber 132 to the respective intake passages130 downstream of the throttle valves 152. Auxiliary air, primarily idleair, can be delivered to the combustion chambers 110 through the AADwhen the throttle valves 152 are placed in a substantially closed orclosed position.

[0052] The AAD preferably comprises an auxiliary air passage, anauxiliary valve and an auxiliary valve actuator. The auxiliary airpassage is branched off to the respective intake passages 130. Theauxiliary valve controls flow through the auxiliary air passage suchthat the amount of air flow can be more precisely controlled.Preferably, the auxiliary valve is a needle valve that can move betweenan open position and a closed position, which closes the auxiliary airpassage. The auxiliary valve actuator actuates the auxiliary valve tometer or adjust an amount of the auxiliary air.

[0053] The engine 32 also comprises an exhaust system that guides burntcharges, i.e., exhaust gases, to a location outside of the outboardmotor 30. Each cylinder bore 104 preferably has two exhaust ports (notshown) defined in the cylinder head member 108. The exhaust ports can beselectively opened and closed by exhaust valves. The exhaust valves areschematically illustrated in FIG. 9, described below, and are identifiedby reference numeral 156. The construction of each exhaust valve and thearrangement of the exhaust valves are substantially the same as theintake valves 134 and the arrangement thereof, respectively.

[0054] An exhaust manifold (not shown) preferably is disposed next tothe exhaust ports (not shown) and extends generally vertically. Theexhaust manifold communicates with the combustion chambers 110 throughthe exhaust ports to collect exhaust gases therefrom. The exhaustmanifold is coupled with the exhaust passage of the exhaust guide member98. When the exhaust ports are opened, the combustion chambers 110communicate with the exhaust passage through the exhaust manifold.

[0055] With particular reference to FIGS. 2, 3, 5, 6 and 8, a valve cammechanism or valve actuator 170 preferably is provided for actuating theintake valves 134 and the exhaust valves 156 (FIG. 9). In theillustrated arrangement, the valve cam mechanism 170 includes an intakecamshaft 172 and an exhaust camshaft 174 both extending generallyvertically and journaled for rotation relative to the cylinder headmember 108. In the illustrated arrangement, bearing caps 176, 178 (FIG.2) journal the camshafts 172, 174 with the cylinder head member 108.

[0056] A camshaft cover member 179 is affixed to the cylinder headmember 108 by bolts 568 (FIG. 8) via a seal member 570 made of, forexample, rubber to define a pair of camshaft chambers 180 together withthe cylinder head member 108. The seal member 570 not only seals butalso prevents the camshaft cover member 179 from vibrating. As shown inFIG. 8, at least a portion 572 of the camshaft cover member 179 abutsthe cylinder head member 108 without interposing the seal member 570.This is advantageous because the camshaft cover member 179 is accuratelypositioned relative to the cylinder head member 108. Each camshaft 172,174 is enclosed within each camshaft chamber 180. Alternatively,separate camshaft cover members can replace the single cover member 180to separately enclose the camshafts 172, 174.

[0057] Each camshaft 172, 174, as shown in FIG. 6, has a plurality ofcams 181 associated with the intake or exhaust valves 134, 156. Each cam181 defines a cam lobe 181 a to push valve lifters 182 that are affixedto the respective ends of the intake valves 134 and exhaust valves 156(FIG. 9) as in any suitable manner. The cam lobes 181 a repeatedly pushthe valve lifters 182 in a timed manner, which is in proportion to theengine speed. The movement of the lifters 182 generally is timed by therotation of the camshafts 172, 174 to actuate the intake valves 134 andthe exhaust valves.

[0058] As shown in FIG. 6, in the illustrated arrangement, a top end ofthe camshaft cover member 179 is nested between an inner surface of thesprocket 188 and an outer surface of a top end of the cylinder block108. Thus, the camshaft cover member 179 is attached to or detached fromthe intake camshaft 172 with the sprocket 188 removed. This arrangementallows the total height of the engine 32 to be shorter.

[0059] With reference to FIG. 3, a camshaft drive mechanism 186 drivesthe valve cam mechanism 170. The intake camshaft 172 and the exhaustcamshaft 174 include an intake driven sprocket 188 positioned atop theintake camshaft 172 and an exhaust driven sprocket 190 positioned atopthe exhaust camshaft 174. The crankshaft 118 has a drive sprocket 192positioned at an upper portion thereof. Of course, other locations ofthe sprockets also can be used. The illustrated arrangement, however,advantageously results in a compactly arranged engine.

[0060] A timing chain or belt 194 is wound around the driven sprockets188, 190 and the drive sprocket 192. The crankshaft 118 thus drives therespective camshafts 172, 174 through the timing chain 194 in the timedrelationship. Because the camshafts 172, 174 must rotate at half of thespeed of the rotation of the crankshaft 118 in the four-cycle combustionprinciple, a diameter of the driven sprockets 188, 190 is twice as largeas a diameter of the drive sprocket 192.

[0061] With reference to FIGS. 3-5, the engine 32 preferably has a portor manifold fuel injection system. The fuel injection system preferablycomprises four fuel injectors 198 with one fuel injector allotted foreach of the respective combustion chambers 110 through suitable fuelconduits. Each fuel injector 198 preferably has an injection nozzledirected toward the associated intake passage 130 adjacent to the intakeports 128. The fuel injectors 198 preferably are mounted on a fuel rail199. Preferably, the fuel rail 199 extends generally vertically and ismounted on the intake manifolds 140. The fuel rail 199 also defines aportion of the fuel conduits.

[0062] A heat exchanger 200 preferably is provided to cool the fuel andextends parallel to the fuel rail 199. The heat exchanger 200 preferablycomprises a pair of fluid pipes, one of which defines part of the fuelconduits and the other defines a water passage through which coolingwater can flow.

[0063] With reference to FIGS. 4 and 5, the illustrated fuel injectionsystem additionally comprises a fuel pump assembly 500 that is actuatedby the intake camshaft 172. The fuel pump assembly 500 is mounted on thecamshaft cover member 179 and is disposed adjacent to the intake cam 181that actuates the intake valve 134 associated with the combustionchamber 110 positioned second from the bottom.

[0064] The fuel pump assembly 500 preferably comprises a bottom housingmember 502, a middle housing member 504 and a top housing member 506.The housing members 502, 504, 506 are coupled together by bolts 508. Thebottom housing member 502 forms a projection 510. The camshaft covermember 179 defines an opening at a support portion 512 thereof and theprojection 510 is fitted into the opening so that the fuel pump assembly500 is mounted on the cover member 179. Fasteners such as bolts can fixthe pump assembly 500 to the cover member 179.

[0065] A diaphragm 516 preferably is provided with a periphery portionthereof interposed between the bottom and middle housing members 502,504. A pump rod 518 depends from the diaphragm 516. A top portion 520 ofthe pump rod 518 preferably supports upper and lower plates 524, 526which together sandwich the diaphragm 516 therebetween. The bottomhousing member 502 defines a guide section 530 that slidably supportsthe top portion 520 of the pump rod 520. A spring 532 urges thediaphragm 516 upwardly such that the lower plate 526 does not abut theguide section 530. The guide section 530 and the projection 510 togetherdefine a recess in which a slider 534 slides. A spring 536 biases theslider 534 downwardly. The slider 534 defines a recess therein in whicha lower portion of the pump rod 520 slides. A lowermost end 538 of theslider 534 protrudes downwardly.

[0066] An arm member 540 is journaled on a support shaft 542 for pivotalmovement about an axis of the shaft 542. The support shaft 542 isaffixed to the bearing cap 178. The lowermost end 538 of the slider 534is biased against a top surface of the arm member 540 by the spring 536.The arm member is thereby biased against the cam 181. The cam 181 thuslifts the slider 534 upwardly when the cam lobe 181 a meets the armmember 540.

[0067] The diaphragm 516 defines a pump chamber 546 together with themiddle housing member 504. The middle housing member 504 and the tophousing member 506 in turn together define an inlet chamber 548 and anoutlet chamber 550 both of which are separated from each other. Theinlet chamber 548 is connected toward a fuel source such as, forexample, a fuel tank, while the outlet chamber 550 is connected towardthe fuel rail 199. The inlet chamber 548 also is connected to the pumpchamber 546 through an inlet path member 552 fitted into an aperturecommunicating with both the inlet and pump chambers 548, 546. The outletchamber 550 also is connected to the pump chamber 546 through an outletpath member 554 fitted into an aperture communicating with both theoutlet and pump chambers 550, 546.

[0068] One end of the inlet path member 552 is open to the inlet chamber548 and another end thereof is closed but one or a plurality of sideopenings are formed in close proximity to this end to communicate withthe pump chamber 546. A flange 558 is provided adjacent to the sideopenings so as to somewhat impede fuel from moving to the pump chamber546. Similarly, one end of the outlet path member 554 is open to thepump chamber 546 and another end thereof is closed but one or more sideopenings are formed in close proximity to this end to communicate withthe outlet chamber 550. A flange 560 is provided adjacent to the sideopenings so as to somewhat impede fuel from moving to the outlet chamber550.

[0069] With the intake camshaft 172 rotating, the cam 181 lifts the armmember 540 at every moment when the cam lobe 181 a meets the arm member540. The arm member 540 thus repeatedly pivots about the axis of thesupport shaft 542 and reciprocally moves the slider 534 together withthe spring 536. The slider 534 pushes the pump rod 518 upwardly when theslider 534 moves upwardly and releases the pump rod 518 when the slider534 moves downwardly so that the pump rod 518 also repeatedly movesupwardly and downwardly. The diaphragm 516, which is affixed to the topportion 520 of the pump rod 518, thus move upwardly and downwardly. Thevolume of the pump chamber 546 thus is repeatedly changed. Accordingly,the fuel in the pump chamber 546 moves into the outlet chamber 550through the outlet path member 554 and the fuel in the inlet chamber 548moves into the pump chamber 546 through the inlet path member 552. Thefuel pump 500 thus can deliver the fuel from the fuel tank to the fuelrail 199.

[0070] The fuel injectors 198 spray fuel into the intake passages 130under control of an ECU 201 (FIG. 9) which preferably is mounted on theengine body 124 at an appropriate location. The ECU 201 controls boththe start timing and the duration of the fuel injection cycle of thefuel injectors 198 so that the nozzles spray a proper amount of the fuelfor each combustion cycle. The fuel injection controller within the ECU201 is illustrated in FIG. 9 with reference numeral 202 and is describedbelow. Of course, the fuel injectors 198 can be disposed for directcylinder injection and carburetors can replace or accompany the fuelinjectors 198.

[0071] With reference to FIGS. 2 and 4, the engine 32 further comprisesan ignition or firing system. Each combustion chamber 110 is providedwith a spark plug 203 that is connected to the ECU 201 (FIG. 9) throughan igniter so that ignition timing is also controlled by the ECU 201.Each spark plug 203 has electrodes that are exposed into the associatedcombustion chamber and are spaced apart from each other with a smallgap. The spark plugs 203 generate a spark between the electrodes toignite an air/fuel charge in the combustion chamber 110 at selectedignition timing under control of the ECU 201.

[0072] In the illustrated engine 32, the pistons 106 reciprocate betweentop dead center and bottom dead center. When the crankshaft 118 makestwo rotations, the pistons 106 generally move from the top dead centerto the bottom dead center (the intake stroke), from the bottom deadcenter to the top dead center (the compression stroke), from the topdead center to the bottom dead center (the power stroke) and from thebottom dead center to the top dead center (the exhaust stroke). Duringthe four strokes of the pistons 106, the camshafts 172, 174 make onerotation and actuate the intake valves 134 and the exhaust valves 156(FIG. 9) to open the intake ports 128 during the intake stroke and toopen exhaust ports during the exhaust stroke, respectively.

[0073] Generally, during the intake stroke, air is drawn into thecombustion chambers 110 through the air intake passages 130 and fuel isinjected into the intake passages 130 by the fuel injectors 198. The airand the fuel thus are mixed to form the air/fuel charge in thecombustion chambers 110. Slightly before or during the power stroke, therespective spark plugs 203 ignite the compressed air/fuel charge in therespective combustion chambers 110. The air/fuel charge thus rapidlyburns during the power stroke to move the pistons 106. The burnt charge,i.e., exhaust gases, then are discharged from the combustion chambers110 during the exhaust stroke.

[0074] During engine operation, heat builds in the engine body 124. Theillustrated engine 32 thus includes a cooling system to cool the enginebody 124. The outboard motor 30 preferably employs an open-loop typewater cooling system that introduces cooling water from the body ofwater surrounding the motor 30 and then discharges the water to the bodyof water. The cooling system includes one or more water jackets definedwithin the engine body 124 through which the water travels to removeheat from the engine body 124. The foregoing heat exchanger 200 can usepart of the water flowing through the cooling system.

[0075] The engine 32 also preferably includes a lubrication system. Aclosed-loop type system preferably is employed in the illustratedembodiment. The lubrication system comprises a lubricant tank defining areservoir, which preferably is positioned within the driveshaft housing54. An oil pump (not shown) is provided at a desired location, such asatop the driveshaft housing 54, to pressurize the lubricant oil in thereservoir and to pass the lubricant oil through a suction pipe towardcertain engine portions, which desirably are lubricated, throughlubricant delivery passages. The engine portions that need lubricationinclude, for example, the crankshaft bearings (not shown), theconnecting rods 120 and the pistons 106. Portions 214 of the deliverypassages (FIG. 2) can be defined in the crankshaft 118. Lubricant returnpassages (not shown) also are provided to return the oil to thelubricant tank for re-circulation.

[0076] A flywheel assembly 216 (FIG. 2) preferably is positioned at anupper end of the crankshaft 118 and is mounted for rotation with thecrankshaft 118. The flywheel assembly 216 comprises a flywheel magnetoor AC generator that supplies electric power to various electricalcomponents such as the fuel injection system, the ignition system andthe ECU 201 (FIG. 9). A protective cover 218, which preferably is madeof plastic, extends over majority of the top surface of the engine 32and preferably covers the portion that includes the fly wheel assembly216 and the camshaft drive mechanism 186.

[0077] The protective cover 218 preferably has a rib 219 (FIG. 4) thatreduces or eliminates the amount of air flowing directly toward theengine portion that has the air induction system 126, i.e., to theportion on the starboard side. The protective cover 218 also preferablyhas a rib 220 (FIG. 2) that substantially or completely inhibits airfrom flowing directly toward a front portion of the engine body 124. Theribs 219, 222 advantageously help direct the airflow around the enginebody 124 to cool the engine body 124. As seen in FIG. 2, a bottomportion, at least in part, of the protective cover 218 desirably is leftopen to allow heat to radiate from the engine 32.

[0078] With reference to FIG. 1, the driveshaft housing 54 depends fromthe power head 50 to support a driveshaft 222 which is coupled with thecrankshaft 118 and which extends generally vertically through thedriveshaft housing 54. The driveshaft 222 is journaled for rotation andis driven by the crankshaft 118. The driveshaft housing 54 preferablydefines an internal section of the exhaust system that leads themajority of exhaust gases to the lower unit 56. An idle dischargesection is branched off from the internal section to discharge idleexhaust gases directly out to the atmosphere through a discharge portthat is formed on a rear surface of the driveshaft housing 54 in idlespeed of the engine 32. The driveshaft 222 preferably drives the oilpump.

[0079] With continued reference to FIG. 1, the lower unit 56 dependsfrom the driveshaft housing 54 and supports a propulsion shaft 226 thatis driven by the driveshaft 222. The propulsion shaft 226 extendsgenerally horizontally through the lower unit 56 and is journaled forrotation. The propulsion device 41 is attached to the propulsion shaft226. In the illustrated arrangement, the propulsion device includes apropeller 228 that is affixed to an outer end of the propulsion shaft226. The propulsion device, however, can take the form of a dualcounter-rotating system, a hydrodynamic jet, or any of a number of othersuitable propulsion devices.

[0080] A transmission 232 preferably is provided between the driveshaft222 and the propulsion shaft 226, which lie generally normal to eachother (i.e., at a 90° shaft angle) to couple together the two shafts222, 226 by bevel gears. The transmission 232 includes a switchovermechanism (not shown) that is configured to change a rotationaldirection of the propeller 228 between forward, neutral or reverse. Theswitchover mechanism typically comprises a dog clutch and a shift unitthat operates the dog clutch. At the forward and reverse positions,which are propulsion positions, the propeller 228 propels the watercraft40 forward and backward, respectively. At the neutral position, which isa-non-propulsion position, the propeller 228 does not propel thewatercraft 40 because the propulsion shaft 226 is disconnected from thedriveshaft 222.

[0081] Preferably, the switchover mechanism is interconnected with thethrottle valve linkage. A single control lever, which is the foregoingthrottle lever, is connected with not only the throttle valve but alsothe switchover mechanism to control both of them in an interrelationshipsuch that the throttle valve is always closed (or almost closed) whenthe transmission is placed in the neutral position by the switchovermechanism, except for an engine racing operation. The throttle linkagecan be released from the switchover mechanism for the racing operation.

[0082] The lower unit 56 also defines an internal section of the exhaustsystem that is connected with the internal section of the driveshafthousing 54. At engine speeds above idle, the exhaust gases generally aredischarged to the body of water surrounding the outboard motor 30through the internal sections and then through a discharge sectiondefined within the hub of the propeller 228. Preferably, the outboardmotor 30 also includes an idle exhaust discharge (not shown) configuredto discharge exhaust gases to the atmosphere at a position above thewaterline WL at idle engine speeds.

YVT Mechanism

[0083] With reference to FIGS. 2-4, 6 and 8 and with additionalreference to FIG. 7, a VVT mechanism 240 is described below.

[0084] The VVT mechanism 240 preferably is configured to adjust theangular position of the intake camshaft 172 relative to the intakedriven sprocket 188 between two limits, i.e., a fully advanced angularposition and a fully retarded angular position. At the fully advancedangular position, the intake camshaft 172 opens and closes the intakevalves 134 at a most advanced timing. In contrast, at the fully retardedangular position, the intake camshaft 172 opens and closes the intakevalves 134 at a most retarded timing.

[0085] The VVT mechanism 240 preferably is hydraulically operated andthus comprises an adjusting section 242, a fluid supply section 244 anda control section 246. The adjusting section 242 sets the intakecamshaft 172 to an angular position in response to a volume of workingfluid that is allotted to two spaces of the adjusting section 242. Thefluid supply section 244 preferably supplies a portion of the lubricant,which is used primarily for the lubrication system, to the adjustingsection 242 as the working fluid. The control section 246 selects therate or amount of the fluid directed to the adjusting section 242 undercontrol of the ECU 201 (FIG. 9).

[0086] With reference to FIG. 7, the adjusting section 242 preferablyincludes an outer housing 250 and an inner rotor 252. The outer housing250 is affixed to the intake driven sprocket 188 by three bolts 254 inthe illustrated arrangement and preferably forms three hydraulicchambers 256 between the three bolts 254. Any other suitable fasteningtechnique and any suitable number of chambers 256 can be used.

[0087] The inner rotor 252 is affixed atop the intake camshaft 172 by abolt 258 (FIG. 6) and has three vanes 260 extending into the respectivechambers 256 of the housing 250. The number of vanes 260 can be variedand the inner rotor 252 can be attached to the camshaft 172 in anysuitable manners.

[0088] With reference to FIG. 7, the vanes 260 preferably extendradially and are spaced apart from each other with an angle of about 120degrees. The two sides of the vane 260, together with walls 262 of eachchamber 256, define a first space S1 and a second space S2,respectively. Seal members 266 carried by the respective vanes 260 abutsan inner surface of the housing 250 and thereby substantially seal thefirst and second spaces S1, S2 from each other.

[0089] The respective first spaces S1 communicate with one anotherthrough respective pathways 270 and a passage 272 that is formed on anupper surface of the rotor 252 and extends partially around the bolt258. The respective second spaces S2 communicate with one anotherthrough respective pathways 274 and a passage 276 which is formed on alower surface of the rotor 252 and extends partially around the bolt258. The passages 272, 276 generally are configured as an incompletecircular shape and can be offset from one another (e.g., a 60 degreeoffset may be used).

[0090] A pathway 278 extends from the passage 272 to a bottom portion ofthe rotor 252 between the ends of the passage 276. A cover member 280preferably is affixed to the outer housing 250 by screws 282 to coverthe bolt 258. The cover member 280 preferably is made of rubber,synthetic resin or sheet metal and can be fitted into an aperture 283without using the screws 282. The passages 272, 276 allow fluidcommunication with the respective pathways 270, 274, 278 during rotationof the camshaft 172.

[0091] With reference to FIGS. 2 and 6, the fluid supply section 244preferably includes a supply passage 284 and two delivery passages 286,288. The supply passage 284 and the delivery passages 286, 288communicate with one another through the control section 246. The supplypassage 284 preferably has a passage portion 284 a (FIGS. 2 and 6)defined in the cylinder head member 108 and a passage portion 284 b(FIG. 2) defined in the bearing cap 176. The passage portion 284 a isconnected to the lubrication system, while the passage portion 284 b isconnected to the control section 246. Thus, the lubricant oil of thelubrication system is supplied to the control section 246 through thefluid supply passage 284.

[0092] The supply passage 284 communicates with the lubrication systemso that a portion of the lubricant oil is supplied to the VVT mechanism240 as working fluid through the passage portions 284 a, 284 b. Becausethe passage portion 284 a is formed by a drilling process in theillustrated embodiment, a closure member 290 closes one end of thepassage portion 284 a. The passage portion 284 b is branched off to acamshaft lubrication passage 284 c (FIG. 6) which delivers lubricant forlubrication of a journal of the camshaft 172.

[0093] The delivery passages 286, 288 preferably are defined in a topportion of the camshaft 172 and the bearing cap 176. A portion of thedelivery passage 286 formed in the camshaft 172 includes a pathway 292that extends generally vertically and that communicates with the pathway278 that communicates with the passage 272 of the first space S1. Thepathway 292 also communicates with a passage 294 that is formed as arecess in the outer surface of the camshaft 172.

[0094] A portion of the delivery passage 288 formed in the camshaft 172,in turn, includes a pathway 296 that extends generally vertically andcommunicates with the passage 276 of the second space S2. The pathway296 also communicates with a passage 298 that is formed as a recess inthe outer surface of the camshaft 172.

[0095] A portion of the delivery passage 286 formed in the bearing cap176 includes a pathway 300 that extends generally vertically andgenerally horizontally to communicate with the passage 294. Similarly, aportion of the delivery passage 288 formed in the bearing cap 176includes a pathway 302 that extends generally vertically and generallyhorizontally to communicate with the passage 298. The other ends of thepathways 300, 302 communicate with a common chamber 304 formed in thecontrol section 246 through ports 306, 308, respectively.

[0096] A seal member 310 (FIG. 6) is disposed between the cylinder headmember 108, the camshaft 172 and the bearing cap 176 to inhibit thelubricant from leaking out. It should be noted that FIGS. 6 and 8illustrate the delivery passages 286, 288 in a schematic fashion. Thepassages 286, 288 do not merge together.

[0097] The control section 246 preferably includes an oil control valve(OCV) 314 (FIG. 8). The OCV 314 comprises a housing section 316 and acylinder section 318. A lower end 319 (FIG. 4) of the protective cover218 covers the housing section 316 so that water, if any, does not tosplash onto the housing section 316. Both the housing and cylindersections 316, 318 preferably are received in the bearing cap 176.Because the sections 316, 318 together extend through a hole of thecamshaft cover member 179, a bellow 320 made of rubber is providedbetween the housing section 316 and the camshaft cover member 179 toclose and seal the hole.

[0098] The cylinder section 318 defines the common chamber 304 thatcommunicates with the supply passage 284 and the delivery passages 286,288. The housing section 316 preferably encloses a solenoid typeactuator, although other actuators of course are available.

[0099] A rod 324 extends into the common chamber 304 from the actuatorand is axially movable therein. The rod 324 has a pair of valves 326,328 and a pair of guide portions 330. The valves 326, 328 and the guideportions 330 have an outer diameter that is larger than an outerdiameter of the remainder portions 331 of the rod 324 and is generallyequal to an inner diameter of the cylinder section 318. The rod 324defines an internal passage 334 extending through the rod 324 andapertures 335 communicating with the passage 334 and the common chamber304 to allow free flow of the fluid in the chamber 304.

[0100] A coil spring 338 is retained in a spring retaining space 339 atan end of the cylinder 318 opposite to the housing section 316 to urgethe rod 324 toward the actuator. The fluid can be drained to thecamshaft chamber 180 through the spring retaining chamber 339 and adrain hole 340.

[0101] The actuator, i.e., solenoid, actuates the rod 324 under controlof the ECU 201 (FIG. 9) so that the rod 324 can take any position in thechamber 304. More specifically, the solenoid pushes the rod 324 toward aposition in compliance with commands of the ECU 201. If a certainposition designated by the ECU 201 is closer to the solenoid than acurrent position, then the solenoid does not actuate the rod 324 and thecoil spring 338 pushes the rod 324 back to the desired position.Alternatively, the solenoid can be configured to pull the rod 324 backto the position.

[0102] The valve 326 can close the port 306 entirely or partially, andthe valve 328 can close the port 308 entirely or partially. The size ofthe openings at the ports 306, 308 determines an amount of the fluidthat is allotted to each delivery passage 286, 288 and to each space S1,S2 in the adjusting section 242. The amount of fluid delivered to eachspace S1, S2 thus determines an angular position of the camshaft 172. Ifmore fluid is allotted to the first space S1 than to the second spaceS2, the camshaft 172 is adjusted closer to the fully advanced position,and vise versa.

[0103] The oil pump pressurizes the lubricant oil to the supply passage284 and further to the common chamber 304 of the cylinder 318.Meanwhile, the ECU 201 (FIG. 9) controls the solenoid. The solenoidmoves the rod 324 and thus adjusts the degree to which the valves 326,328 allow the chamber to communicate with the ports 306, 308,respectively. The ECU 201 thereby controls the angular position of thecamshaft 172. Preferably, a drain is provided to allow the working fluidto drain from the space that is being evacuated while pressurizedworking fluid flows into the opposing space.

[0104] In one mode of operation, for example, the working fluid is fedto the common chamber 304 of the cylinder 318. Thus, the common chamber304 has a positive pressure. To move the camshaft 172 in a firstdirection relative to the input sprocket 188, the common chamber 304 islinked with the delivery passage 286 while the other of the deliverypassage 288 is linked to a drain. Thus, pressurized fluid will flow intothe first space S1 while fluid will be displaced from the second spaceS2. The displaced fluid flows through the passage 334 and to the drain340 and thereby returns to the lubrication system. Once the desiredmovement has occurred, the rod 324 is returned to a neutral position inwhich the common chamber 304 is no longer communicating with either ofthe delivery passages 286, 288. Additionally, in the neutral position,neither of the delivery passages 286, 288 communicates with the drain inone particularly advantageous arrangement. Of course, by varying theplacement and size of the seals, a constant flow can be produced fromsupply to drain while the rod 324 is in a neutral position. Also, aconstant flow into the delivery lines also can be constructed. In theillustrated arrangement, however, no flow preferably occurs with thesystem in a neutral position.

[0105] In general, the engine and the VVT mechanism are disclosed in,for example, a co-pending U.S. application filed Jun. 11, 2001, titledFOUR-CYCLE ENGINE FOR MARINE DRIVE, which Ser. No. is 09/878,323, theentire contents of which is hereby expressly incorporated by reference.

[0106] With reference to FIGS. 2, 4 and 11, in the illustratedarrangement, the camshaft cover member 179 preferably defines an accessopening 574 below the VVT mechanism 240 and above the fuel pump assembly500. Preferably, the opening 574 is disposed above the top end 70 of thebottom cowling member 66. A closure member 576 is detachably affixed toa mount portion 578 of the camshaft cover member 179 by bolts 580 via aseal member or gasket 582 to close the opening 574. The opening 574preferably has a size through which a tool such as, for example, awrench can pass through. The intake camshaft 172 preferably forms ahexagonal portion 586 at which the wrench is engageable.

[0107] With the closure member 576 removed, the user, operator,repairperson or mechanic can insert the wrench through the slot 574. Thewrench is engaged with the hexagonal portion 586 of the camshaft 172 tofix the camshaft 172 (i.e., to prevent the camshaft 172 from rotating).

[0108] The repairperson, for example, thus can easily disassemble thesprocket 188 from the camshaft 172 or assemble the sprocket 188 theretofor maintenance service or for other purposes. Because the drain oilaccumulated within the camshaft chamber 180 does not spill out, theengine 32 is less likely to be stained by the oil and the repairpersondoes not need to pay special attention to prevent a large oil spill.

[0109] Because the top end of the camshaft cover member 179 is nested inthe sprocket 188 in the arrangement, the illustrated sprocket 188 shouldbe disassembled from the camshaft 172 before the cover member 179 isremoved. Similarly, in this situation, the wrench inserted through theslot 574 to prevent the camshaft from rotating. The repairperson thuscan work easily without the need for a special test for preventing thetiming chain or belt 194 (FIG. 3) from moving or preventing the vanes260 from rotating. Accordingly, the amount of labor needed can bereduced.

[0110] In addition, no large change in configuration on the camshaft oron components around the camshaft is necessary and an ordinary tool suchas the wrench can be used. Thus, the outboard motor does not need toprovide a large space for a special construction and does not requireadditional labor for the maintenance service.

[0111] Other polygon shaped portions can replace the hexagonal portion586 of the camshaft 172. For example, a triangular shape or arectangular shape can be applied as the polygon shape.

[0112] In addition, the access opening 574 can be in the fan of, forexample, a slot, a circular, or a rectangular configuration.

Control System

[0113] With reference to FIG. 9, a valve timing control system of theVVT mechanism 40 using the ECU 201 is described below.

[0114]FIG. 9 schematically illustrates the engine 32. The illustratedECU 201 adjusts the valve timing of the intake valves 134 by changingthe angular positions of the intake camshaft 172 relative to thesprocket 188 through the VVT mechanism 40. The ECU 201 also controls thefuel injectors 198 using the fuel injection control unit 202. The ECU201 is connected to the OCV 314 as the control section 246 of the VVTmechanism 40 and the fuel injectors through control signal lines.

[0115] In order to control the VVT mechanism 40 and the fuel injectors198, the ECU 201 can employ various sensors which sense operationalconditions of the engine 32 and/or the outboard motor 30. In the presentsystem, the ECU 201 uses a camshaft angle position sensor 350, acrankshaft angle position sensor 352, a throttle position sensor (orthrottle valve opening degree sensor) 354 and an intake pressure sensor356. The ECU 201 is connected to the sensors 350, 352, 354, 356 throughsensor signal lines.

[0116] With reference to FIGS. 2, 4 and 10, the camshaft angle positionsensor 350 preferably is associated with the intake camshaft 172 tosense an angular position of the intake camshaft 172 and sends acamshaft angle position signal to the ECU 201 through the signal line.

[0117] The camshaft position sensor 350 preferably is positionedadjacent to a portion of the camshaft 172 located between the second andthird cylinders of the engine 32. That is, the sensor 350 is placedbelow the housing section 316 of the OCV 314 of the VVT mechanism 240,more specifically, below the opening 574, and above the fuel pumpassembly 500. The sensor 350 preferably is located above the top end 70of the bottom cowling member 66. The position sensor 350 preferably ismounted on a mount portion 600 of the camshaft cover member 179 with aflange portion 602 of the sensor 350 affixed to the mount portion 600 bya bolt 604. A longitudinal axis 606 of the position sensor 350preferably extends generally horizontally and generally parallel to thecenter vertical plane VP.

[0118] A projection 610 is formed on a surface of the intake camshaft172 close proximately to a tip portion of the camshaft position sensor350. When the camshaft 172 rotates, the projection 610 approaches to andrecedes from the tip portion of the sensor 350 for every rotation of thecamshaft 172. The sensor 350 detects the approach or receding of theprojection 610 and generates the signal indicative of the camshaftangular position.

[0119] The positioning of the camshaft angle position sensor 350 isadvantageous because the user, operator, mechanic, or repairperson caneasily access the sensor 350 for maintenance or for other purposes bymerely detaching the upper cowling member 64. Nothing conceals thesensor 350.

[0120] The sensor 350 is not obstructive to the VVT mechanism 240because the sensor 350 is disposed completely below the VVT mechanism240. In other words, the VVT mechanism 240 can be disposed at a mostpreferred position without being obstructed by the sensor 350.

[0121] In addition, because of using a space between the VVT mechanism240 and the fuel pump assembly 500, the positioning of the sensor 350can contribute to make the outboard motor 30 compact.

[0122] The positioning of the sensor 350 relative to the camshaft 172 isaccurate because the sensor 350 is mounted on the camshaft cover member179 which abuts the cylinder head member 108 at least at the portion 572without interposing the seal member 570.

[0123] Further, vibration of the engine 32 is inhibited from beingconducted to the sensor 350 because of the seal member 570.

[0124] With reference to FIG. 9, the crankshaft angle position sensor352 is associated with the crankshaft 118 to sense an angular positionof the crankshaft 118 and sends a crankshaft angle position signal tothe ECU 201 through the signal line. Any conventional crankshaft angleposition sensors and any conventional arrangements thereof can beapplied.

[0125] Both the camshaft angle position sensor 350 and the crankshaftangle position sensor 352 in the present system generate pulses as therespective signals. The pulse of the camshaft position sensor 350 cangive an actual angular position of the camshaft 172. The crankshaftposition signal together with the camshaft position signal allows theECU 201 to accurately determine the position of the camshaft 172 inrelation to the crankshaft 118.

[0126] With continued reference to FIG. 9, the throttle position sensor354 preferably is disposed atop the valve shaft 154 to sense an angularposition between the open and closed angular positions of the throttlevalves 152 and sends a throttle valve position signal to the ECU 201through the signal line.

[0127] The intake sensor 356 preferably is disposed either within one ofthe intake passages 130 or within the plenum chamber 132 to sense anintake pressure therein. Because the respective intake passages 130 areformed such that each generally is the same size as the others, andbecause the plenum chamber 132 collects a large volume of air that issupplied to each of the intake passages 130, every passage 130 hassubstantially equal pressure and a signal of the intake pressure sensor356 thus can represent a condition of the respective pressure. Thus, itshould be appreciated that a single pressure sensor or multiple pressuresensors can be used.

[0128] The throttle valve position sensor 354 and the intake pressuresensor 356 preferably are selected from a type of sensor that indirectlysenses an amount of air in the induction system. Another type of sensorthat directly senses the air amount, of course, can be applicable. Forexample, moving vane types, heated wire types and Karman Vortex types ofair flow meters also can be used.

[0129] The operator's demand or engine load, as determined by thethrottle opening degree, is sensed by the throttle position sensor 354.Generally, in proportion to the change of the throttle opening degree,the intake air pressure also varies and is sensed by the intake pressuresensor 356. The throttle valve 152 (FIG. 3) is opened when the operatoroperates the throttle lever to increase power output of the engine 32and thus the speed of the watercraft 40. The intake pressure almostsimultaneously decreases as the throttle valve 152 opens.

[0130] The engine load can also increase when the associated watercraft40 is moving against wind. In this situation, the operator also operatesthe throttle lever to recover the speed that may be lost. Therefore, asused in this description, the term “acceleration” means not only theacceleration in the narrow sense but also the recovery of speed by theoperator in a broad sense. Also, the term “sudden acceleration” meansthe sudden acceleration in the narrow sense and a quick recovery ofspeed by the operator in a broad sense.

[0131] The signal lines preferably are configured with hard-wires orwire-harnesses. The signals can be sent through emitter and detectorpairs, infrated radiation, radio waves or the like. The type of signaland the type of connection can be varied between sensors or the sametype can be used with all sensors which are described above andadditional sensors described below.

[0132] Signals from other sensors or control signals also can be usedfor the control by the ECU 201. In the present control system, varioussensors other than the sensors described above are also provided tosense the operational condition of the engine 32 and/or the outboardmotor 30. For example, an oil pressure sensor 360, a water temperaturesensor 362, an engine body temperature sensor 364, a knock sensor 366,an oxygen sensor 370 for determining a current air/fuel ratio, atransmission position sensor 372, a transmission position changeoperation sensor 374, and an intake air temperature sensor 376 areprovided in the present control system. The sensors except for thetransmission sensor 372 and the transmission position change operationsensor 374 can sense the operational conditions of the engine 32 andsend signals to the ECU 201 through respective sensor signal lines. Thetransmission position sensor 372 senses whether the transmission 232(FIG. 1) is placed at the forward, neutral or reverse position and sendsa transmission position signal to the ECU 201 through the signal line.The transmission position change operation sensor 374 senses whether thetransmission position change operation is conducted and sends atransmission position change operation signal to the ECU 201 through thesignal line. An ignition control signal 378, a fuel injection controlsignal 380, and an AAD control signal 382 are also used by the ECU 201for control of the spark plugs 203 (FIG. 2), the fuel injectors 198, andthe AAD (not shown), respectively. The foregoing sensors 350-376 and thecontrol signals 378-382, in a broad sense, define sensors 380 that senseoperational conditions of the engine and/or the outboard motor.

[0133] The ECU 201 can be designed as a feedback control device usingthe signals of the sensors. The ECU 201 preferably has a centralprocessing unit (CPU) and some storage units which store various controlmaps defining relationships between parameters such as, for example, theengine speed, the throttle valve position and the intake pressure(and/or an amount of intake air) to determine an optimum controlconditions. The ECU 201 then controls the VVT mechanism 40, the fuelinjectors 198 and other actuators in accordance with the determinedcontrol condition.

[0134] The fuel injection control unit 202 can be in the form of ahard-wired circuit, a dedicated processor and memory, or a generalpurpose processor and memory running one or a plurality of controlprograms. Other units, described below, can also be constructed as ahard-wired circuit, a dedicated processor and memory, or a generalpurpose processor and memory running one or a plurality of controlprograms. However, for easier understanding of the reader, the unitswill be described as if they were discriminate and substantial units.The illustrated fuel injection control unit 202 controls the fuelinjectors 198 using at least the throttle position signal from thethrottle position sensor 354 and the intake pressure signal from theintake pressure sensor 356.

[0135] The ECU 201 preferably comprises, other than the fuel injectioncontrol unit 202, an actual camshaft angular position calculation(ACAPC) unit 384, an engine speed calculation unit 386, a targetcamshaft angular position calculation (TCAPC) unit 388, and a controlvalue calculation unit 390. The TCAPC unit 388 and the control valuecalculation unit 390 together form an OCV control section 392 in theillustrated ECU configuration.

[0136] The ACAPC unit 384 preferably receives the actual camshaftangular position signal from the camshaft angle position sensor 350 andthe crankshaft angular position signal, which gives two possible rangesof camshaft angular position, from the crankshaft angle position sensor352. The ACAPC unit 384 then calculates a deviation value whichindicates how much the actual camshaft angular position deviates withinthe two possible ranges of camshaft angular position.

[0137] The engine speed calculation unit 386 receives the crankshaftangular position signal from the crankshaft angle position sensor 352and calculates an engine speed using the signal versus time.

[0138] The TCAPC unit 388 receives the deviation value from the ACAPCunit 384, the engine speed from the engine speed calculation unit 386and at least one of the throttle valve opening degree signal from thethrottle valve position sensor 354 and the intake pressure signal fromthe intake pressure sensor 356. The TCAPC unit 388 then calculates atarget camshaft angular position based upon the deviation value, theengine speed and either the throttle valve opening degree signal or theintake pressure signal.

[0139] The control value calculation unit 390 receives the targetcamshaft angular position from the TCAPC unit 388 and calculates acontrol value of the OCV 314 of the VVT mechanism 40. That is, thecontrol value calculation unit 390 determines how much fluid should bedelivered to either the space S1 or the space S2 of the adjustingsection 242 of the VVT mechanism 40 based upon the target camshaftangular position.

[0140] Under a normal running condition and an ordinary accelerationcondition (i.e., not sudden acceleration condition), the ECU 201preferably uses either a combination of the throttle valve openingdegree signal with the engine speed signal (α-N method) or a combinationof the intake pressure signal with the engine speed signal (D-j method)to calculate the target camshaft angular position. Otherwise, the ECU201 can use a mixed combination of the α-N method and the D-j methodunder the normal running condition or the ordinary accelerationcondition. The α-N method, the D-j method and the mixed combinationthereof are disclosed in, for example, a co-pending U.S. applicationfiled Feb. 14, 2002, titled CONTROL SYSTEM FOR MARINE ENGINE, which Ser.No. is 10/078,275, the entire contents of which is hereby expresslyincorporated by reference. An air amount signal sensed by the air flowmeter noted above can be applied additionally or instead either theintake pressure signal or the throttle opening degree signal.

[0141] Under a sudden acceleration condition, the illustrated ECU 201uses only the throttle opening degree signal. That is, the ECU 201always determines, at least prior to controlling the OCV 314 with theOCV control section 392, whether the operator wishes sudden accelerationor not. The sudden acceleration condition preferably is determined whena change rate of the throttle opening degree signal, a change rate ofthe intake pressure signal or a change rate of the engine speedcalculated by the engine speed calculation unit 386 becomes greater thana predetermined magnitude. A change rate of the air amount signal alsocan be used to determine the sudden acceleration condition.Theoretically, the predetermined magnitude can be set at any magnitudelarger than zero.

[0142] Of course, the foregoing description is that of preferredcontrols having certain features, aspects and advantages in accordancewith the present invention. Various changes and modifications also maybe made to the above-described controls without departing from thespirit and scope of the invention, as defined by the claims.

What is claimed is:
 1. An internal combustion engine comprising an engine body, a movable member movable relative to the engine body, the engine body and the movable member together defining a combustion chamber, the engine body defining intake and exhaust ports communicating with the combustion chamber, an air induction system communicating with the combustion chamber through the intake port, an exhaust system communicating with the combustion chamber through the exhaust port, an intake valve arranged to move between an open position and a closed position, an exhaust valve arranged to move between an open position and a closed position, a camshaft configured to actuate either the intake valve or the exhaust valve, the camshaft extending generally vertically, and a member configured to engage the engine body so as to enclose the camshaft, the member defining an opening through which a tool can pass, the tool being configured to prevent the camshaft from rotating.
 2. The engine as set forth in claim 1 additionally comprising a change mechanism arranged to change an angular position of the camshaft, the opening being disposed below the change mechanism.
 3. The engine as set forth in claim 1 additionally comprising a fuel pump mechanically interfaced with the camshaft, the opening being disposed above the fuel pump.
 4. The engine as set forth in claim 1, wherein the opening comprises a slot.
 5. The engine as set forth in claim 1, wherein the camshaft forms an engaging portion engageable with the tool to prevent the camshaft from rotating.
 6. The engine as set forth in claim 5, wherein the engaging portion has a polygon configuration.
 7. The engine as set forth in claim 1 additionally comprising a closure member configured to close the opening.
 8. The engine as set forth in claim 7, wherein the closure member is affixed to the member via a seal.
 9. The engine as set forth in claim 1, additionally comprising a crank shaft, the crank shaft extending vertically.
 10. The engine as set forth in claim 9, wherein the opening is above a lower end of the member.
 11. A marine drive comprising an internal combustion engine, and a cowling assembly configured to surround the engine, the engine comprising an engine body, a movable member movable relative to the engine body, the engine body and the movable member together defining a combustion chamber, the engine body defining intake and exhaust ports communicating with the combustion chamber, an air induction system communicating with the combustion chamber through the intake port, an exhaust system communicating with the combustion chamber through the exhaust port, an intake valve arranged to move between an open position and a closed position, an exhaust valve arranged to move between an open position and a closed position, a camshaft configured to actuate at least one of the intake valve and the exhaust valve, the camshaft extending generally vertically, and a member arranged to engage the engine body so as to enclose the camshaft, the member defining an opening, the cowling assembly comprising top and bottom cowling members, the top cowling member being detachably coupled with the bottom cowling member, the opening being disposed above a top end of the bottom cowling member.
 12. The marine drive as set forth in claim 11, wherein the opening has a size through which a tool can pass, the tool being adapted to prevent the camshaft from rotating.
 13. The marine drive as set forth in claim 11 additionally comprising a change mechanism arranged to change an angular position of the camshaft, the opening being disposed below the change mechanism.
 14. The marine drive as set forth in claim 11, wherein the camshaft forms an engaging portion engageable with the tool to prevent the camshaft from rotating.
 15. The marine drive as set forth in claim 14, where in the engaging portion has a polygon configuration.
 16. The marine drive as set forth in claim 11 additionally comprising a closure member configured to close the opening. 